JP2001095097A - Electret capacitor microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extremely thin electret capacitor microphone. SOLUTION: In this electret capacitor microphone, an electret layer 6 is arranged inside of a conductive capsule 11, an oscillation film 2 is arranged to face this electret layer and an electrical signal generated by this oscillation film is impedance-converted by an active element 7 consisting of an FET to be fetched. In the microphone, a printed wiring board for supporting the active element is obtained by laminating and associating a first printed wiring board 8A for supporting the active element and a second print wiring board 8B which has an outer peripheral shape larger than that of the first printed wiring board and is provided with a through-hole 15A for putting the active element through, and the opening end part of the capsule is caulked to the periphery of the second printed wiring board extending to the outer periphery of the first printed wiring board to arrange the first printed wiring board in the outside of the capsule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electret condenser microphone which is used by being mounted on, for example, a portable telephone or a video camera, etc., and particularly to an object for thinning.

[0002]

2. Description of the Related Art Electret condenser microphones are roughly classified into a back electret type and a front electret type. FIG. 10 shows the structure of a back electret condenser microphone. In the figure, reference numeral 1 denotes a front cloth made of, for example, cloth or the like, 2 denotes a vibrating membrane, 3 denotes a vibrating membrane ring that supports the vibrating membrane 2, and 4 denotes a back electrode (fixed electrode) which faces the vibrating membrane 2 to form a capacitor. ), 5 is a spacer interposed between the vibrating film 2 and the back electrode 4 to form a gap between the vibrating film 2 and the back electrode 4, 6 is attached to the back electrode 4 by vapor deposition or the like, and has a thickness. Electret layer charged in the direction,
Reference numeral 7 denotes an active element formed by, for example, an FET or the like, which converts an electric signal generated in the back electrode 4 into an impedance, and 8 denotes a printed wiring board that supports the active element 7.
Reference numeral 9 denotes a back electrode holder for maintaining a gap between the printed wiring board 8 and the back electrode 4, reference numeral 10 denotes a connection terminal for electrically connecting an input terminal of the active element 7 to the back electrode 4, and reference numeral 11 denotes a vibration membrane ring 3. ,
A capsule for caulking and housing the spacer 5, the back electrode 4, the back electrode holder 9, and the printed wiring board 8 in a stacked state is shown.

The capsule 11 is formed of a conductive metal plate, and is formed of a cylindrical body having one end serving as a closing plate 11A. A sound hole 12 is formed in the closing plate 11A, and a sound is introduced from outside through the sound hole 12 to vibrate the diaphragm 2. FIG. 11 shows the structure of a front electret condenser microphone. Parts corresponding to those in FIG. 10 are denoted by the same reference numerals. The feature of the front electret type is that the electret layer 6 is deposited on the front side of the capsule 11, that is, on the inner surface of the closing plate 11A.

By arranging the vibration film 2 facing the electret layer 6 with the spacer 5 interposed therebetween and maintaining a slight gap from the electret layer 6, the gap between the vibration film 2 and the printed wiring board 8 is reduced. Since only a small margin is required for the height H of the active element 7, there is an advantage that the entire thickness can be reduced as compared with the back electret type condenser microphone shown in FIG.

[0005]

As shown in FIG. 11, the front electret condenser microphone has an advantage that it can be made thinner due to its structure. However,
Practically, the size of the equipment to be mounted is being reduced, so that further miniaturization, particularly thinning is required. An object of the present invention is to provide a conventional front electret condenser microphone shown in FIG. 11 in which the ratio of the thickness of the printed wiring board 8 to the total thickness is high, and the addition of the capsule 11 to the exposed surface of the printed wiring board 8. Focusing on the fact that there is a dead space DS corresponding to the thickness of the fastening piece 11B, it is intended to achieve a reduction in thickness by effectively utilizing the dead space DS.

[0006]

According to a first aspect of the present invention, a vibrating membrane ring for supporting a vibrating membrane, an active element for converting an electric signal generated in the vibrating membrane into impedance and extracting the same, and supporting the active element are provided. A printed wiring board and a tubular body formed by a conductive plate, one end of which is a closed surface, a sound hole is formed in the closed surface of the tubular body,
A vibrating membrane ring that supports the vibrating membrane while maintaining a slight gap from the inner surface of the closed surface is disposed, a printed wiring board is disposed on the opening side of the tubular body, and the end on the opening side is the printed wiring board. In an electret condenser microphone composed of a capsule which is crimped on a plate surface and stores a vibrating membrane ring and a printed wiring board in a stacked manner, the printed wiring board is a printed wiring for electrically connecting and supporting active elements. An electret condenser microphone including a first printed wiring board on which a conductor is formed and a second printed wiring board laminated on the first printed wiring board and formed with a through hole through which an active element is formed is proposed.

According to a second aspect of the present invention, in the electret condenser microphone according to the first aspect, the second printed wiring board has a peripheral shape smaller than the peripheral shape of the first printed wiring board, and the caulking piece of the capsule is The present invention proposes an electret condenser microphone having a structure that is crimped to the periphery of the first printed wiring board. According to a third aspect of the present invention, in any one of the electret condenser microphones according to the first or second aspect, an electret layer is formed on the inner surface of the closed surface of the capsule, and the electret layer and the diaphragm are opposed to each other. We propose an electret condenser microphone with a condenser structure.

[0008]

According to the first aspect of the present invention, the thickness of each of the first printed wiring board and the second printed wiring board is selected to be about 1/2 of the thickness of the printed wiring board 8 shown in FIGS. Then, if you want to obtain the same thickness by laminating,
Since the active element is mounted on the printed wiring formed on the first printed wiring board through the through hole formed on the second printed wiring board, the height H of the active element in the capsule is reduced by the thickness of the second printed wiring board. can do. As a result, there is an advantage that the entire thickness can be made smaller than the thickness of the conventional front electret condenser microphone shown in FIG.

According to the structure of the electret condenser microphone proposed in claim 2 of the present invention, the outer peripheral shape of the second printed wiring board is made smaller than the outer peripheral shape of the first printed wiring board. 2. The electret condenser microphone proposed in claim 1, wherein the peripheral plate surface is exposed at the opening end of the capsule, and the opening end of the capsule is bent and crimped to the exposed plate surface of the second printed wiring board. Can be made even thinner.

That is, according to the electret condenser microphone proposed in claim 2 of the present invention, FIG.
The dead space DS existing in the conventional front electret condenser microphone shown in FIG. 1 is used for the storage location of the first printed wiring board, so that the thickness of the printed wiring board 8 is equivalent to the thickness of the front electret condenser microphone shown in FIG. The advantage that the thickness can be reduced by the amount is obtained.

According to the structure of the electret condenser microphone proposed in claim 3 of the present invention, the electret layer is attached to the inner surface of the closing plate of the capsule, and the vibrating film is arranged so as to face the electret layer. Since the present invention is applied to a so-called front electret condenser microphone in which a capacitor is constituted by a film and an electret layer, it is possible to provide an electret condenser microphone thinner than a conventional front electret condenser microphone.

[0012]

FIG. 1 shows an embodiment of an electret condenser microphone proposed in claim 1 of the present invention. Parts corresponding to FIGS. 10 and 11 are denoted by the same reference numerals. The feature of the electret condenser microphone proposed in the present invention is that the printed wiring board 8 supporting the active element 7 has a two-layer structure of printed wiring boards 8A and 8B, and the components such as the active element 7 are arranged on one printed wiring board 8A. (Hereinafter referred to as the first printed wiring board),
The other printed wiring board 8B (hereinafter, referred to as a second printed wiring board) is formed with a through hole through which components such as the active element 7 penetrate, and its periphery is projected from the outer periphery of the first printed wiring board. The opening end of the capsule is crimped to the part. With this structure, the second printed wiring board 8B
Functions as a member for fixing the first printed wiring board 8A to the capsule 11.

That is, as shown in FIG. 2, the printed wiring conductors 14A, 1A are provided on one surface of the first printed wiring board 8A.
4B, 14C, and the printed wiring conductors 14A,
The second printed wiring board 8B is laminated on the formation surface of 14B, 14C. The first printed wiring board 8A and the second printed wiring board 8B are united by an adhesive. 2 and 3 show the front and back structures of the first printed wiring board 8A.
FIG. 2 shows the structure of the front surface (joining surface) on which the printed wiring conductors 14A, 14B, 14C are formed, and FIG. 3 shows the structure of the rear surface. On the back side, a first common electrode 17 is formed on the periphery, and a signal electrode 18 is formed in the center surrounding the through hole SH2. The through hole SH2 penetrates through the insulating plate of the first printed wiring board 8A and is connected to the printed wiring conductor 14B shown in FIG.

A through hole SH1 is formed in the region of the first common electrode 17. This through hole SH1 penetrates through the insulating plate of the first printed wiring board 8A and is connected to the printed wiring conductor 14C shown in FIG. FIG. 4 shows a state where the second printed wiring board 8B shown in FIG. 5 is joined to the front side (the surface shown in FIG. 2) of the first printed wiring board 8A shown in FIG.

FIGS. 5 and 6 show the structure of the front and back surfaces of the second printed wiring board 8B. FIG. 5 shows the structure on the back side (back side), and FIG. 6 shows the structure on the front side (the side facing the diaphragm 2). In this example, a case where the second common electrode 19 is formed in a ring shape on the back side of the second printed wiring board 8B avoiding the through hole SH3 is shown. The projection 19A of the second common electrode 19 is in electrical contact with the through hole SH1 shown in FIGS. 2 and 3, and is maintained electrically integrated with the first common electrode 17 and the printed wiring conductor 14C.

The through hole SH3 contacts the printed wiring conductor 14A shown in FIG.
6 is electrically connected to a gate ring 21 formed on the front side shown in FIG. The gate ring 21 contacts the conductive washer 13 (see FIG. 1) in the capsule 11 and is electrically connected to the diaphragm 3 through the conductive washer 13 and the diaphragm ring 3.

An electret layer 6 is formed on the inner surface of the closing plate 11A of the capsule 11, and the electret layer 6 and the vibrating film 2 face each other at a predetermined interval depending on the thickness of the spacer 5 (see FIG. 1). Is held. Therefore,
A capacitor is formed between the diaphragm 2 and the closing plate 11A of the capsule 11. That is, the closing plate 11A functions as a fixed electrode. The capsule 11 is electrically connected by crimping to a second common electrode 19 formed in a ring shape on the periphery of the second printed wiring board 8B on the opening end side.

FIG. 7 shows a state where the second printed wiring board 8B shown in FIG. 6 is placed on the surface of the first printed wiring board 8A shown in FIG. When viewed from the back side in a state where the first printed wiring board 8A and the second printed wiring board 8B are laminated and united, the periphery of the second printed wiring board 8B protrudes from the periphery of the first printed wiring board 8A as shown in FIG. The second common electrode 19 is disposed so as to be exposed at the protruding portion.

Therefore, by bending the open end of the capsule 11 and crimping it to the exposed surface of the second common electrode 19, the electret layer 6 is connected to the common potential through the capsule 11, and the electric circuit shown in FIG. You. As is apparent from this electric circuit, when the vibration film 2 vibrates by sound, an electric signal is generated on the vibration film 2 by static electricity charged on the electret layer 6, and the electric signal is impedance-converted by the active element 7. It is output to the outside through the through holes SH1 and SH2.

As is apparent from the above description, according to the embodiment shown in FIG. 1, the gap G (see FIG. 1) between the plate surface of the second printed wiring board 8B and the diaphragm inside the capsule.
) Can be made smaller than the height H of the active element 7, so that the total thickness T1 of the capsule 11 can be made smaller than the thickness of the conventional front electret condenser microphone.

In other words, the first printed wiring board 8A supporting the electric component is conventionally provided with the dead space DS (FIG. 11).
And the second printed wiring board 8
B simply acts as a member for supporting the first printed wiring board 8A. As a result, the second printed wiring board 8B can be seen as a member that does not affect the thickness in the capsule.

Therefore, in the electret condenser microphone according to the present invention shown in FIG. 1, the thickness of the printed wiring board 8 can be regarded as zero inside the capsule 11, and compared with the conventional front electret condenser microphone shown in FIG. As a result, the effect that the printed wiring board 8 can be made thinner by the thickness of the printed wiring board 8 is obtained.

[0023]

Modified Embodiment The embodiment shown in FIGS. 1 to 7 has been described with reference to the most preferred embodiments in consideration of claims 1, 2 and 3. FIG. 9 shows an embodiment corresponding to claim 1 of the present invention. Show. In this embodiment, a case is shown in which the first printed wiring board 8A and the second printed wiring board 8B have the same outer peripheral shape, and the opening end of the capsule 11 is crimped to the first printed wiring board 8A.

Even with this structure, the second printed wiring board 8B has a through hole 15 through which components such as the active element 7 penetrate.
A and 15B, and the components are substantially mounted on the first printed wiring board 8A. Therefore, in the capsule 11, only the thickness of the first printed wiring board 8A is added, and The gap G between the plate surface and the diaphragm 2 is smaller than the height H of the active element 7 in this example, which is the highest among the components.

Therefore, even in the case of the structure of this embodiment, the printed wiring board 8 has a larger thickness than the conventional front electret type condenser microphone shown in FIG.
The advantage is obtained that the thickness can be reduced by about の of the thickness of the substrate. Moreover, the first printed wiring board 8A and the second printed wiring board 8B are laminated and united, despite the fact that the thickness of the printed wiring board 8 is substantially half the thickness of the conventional printed wiring board. The printed wiring board 8A is reinforced,
It has the same strength as the printed wiring board 8 having the conventional structure.

[0026]

As described above, according to the present invention, the thickness of the printed wiring board 8 is not included at all in the capsule 11, or the thickness of the printed wiring board 8 is set to a half of the thickness of the conventional printed wiring board 8. Capsule 11
Can be made thinner than before. Incidentally, a condenser microphone having an outer diameter of 6 mmφ and a thickness of 1 mm of the capsule 11 can be manufactured.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view for explaining a most preferred embodiment of the present invention.

FIG. 2 is a plan view for explaining the structure on the front side of a first printed wiring board used in the embodiment shown in FIG. 1;

FIG. 3 is a back view for explaining the structure on the back side of FIG. 2;

FIG. 4 is a rear view of a state in which a first printed wiring board and a second printed wiring board used in the embodiment shown in FIG. 1 are stacked;

FIG. 5 is a back view for explaining the structure on the back side of the second printed wiring board used in the embodiment shown in FIG. 1;

FIG. 6 is a plan view for explaining the structure of the front side surface of FIG. 5;

FIG. 7 is a plan view of a first printed wiring board and a second printed wiring board used in the embodiment shown in FIG.

FIG. 8 is a connection diagram for explaining an electric circuit structure of the embodiment shown in FIG. 1;

FIG. 9 is an enlarged sectional view for explaining a modified embodiment of the present invention.

FIG. 10 is an enlarged sectional view for explaining the structure of a conventional back electret condenser microphone.

FIG. 11 is an enlarged sectional view for explaining the structure of a conventional front electret condenser microphone.

[Explanation of symbols]

 2 Vibration Film 3 Vibration Film Ring 5 Spacer 6 Electret Layer 7 Active Element 8 Printed Wiring Board 8A First Printed Wiring Board 8B Second Printed Wiring Board 11 Capsule 11A Closing Plate 11B Clamping Piece 12 Sound Hole 13 Conductive Washers 14A, 14B, 14C Printed wiring conductor SH1, SH2, SH3 Through hole 15A, 15B Through hole 16 Capacitor 17 First common electrode 18 Signal electrode 19 Second common electrode

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kensuke Nakanishi 3024-38 Nakayama, Kurate-cho, Fukuoka Prefecture Inside Shiden Kyushu Co., Ltd. F-term in Shiden Kyushu Co., Ltd. (reference) 5D021 CC08 CC11 CC15 CC16 CC19

Claims (3)

[Claims] 1. A vibrating membrane ring supporting a vibrating membrane, an active element for converting an electric signal generated in the vibrating membrane into impedance and taking out the same, a printed wiring board supporting the active element, and a conductive plate, One end is constituted by a cylindrical body having a closed surface, a sound hole is formed in the closed surface of the cylindrical body, and the vibrating membrane ring is disposed while maintaining a slight gap with the inner surface of the closed surface. The printed wiring board is arranged on the opening side of the tubular body, the end on the opening side is crimped to the plate surface of the printed wiring board, and the vibrating membrane ring and the printed wiring board are laminated. And an enclosing capsule, wherein the printed wiring board is provided with a printed wiring conductor for electrically connecting the active element. A printed wiring board is laminated on the first printed circuit board, an electret condenser microphone which is characterized by being composed by a second printed circuit board through hole through which the said active devices are formed. 2. The electret condenser microphone according to claim 1, wherein the first printed wiring board has a peripheral shape smaller than a peripheral shape of the second printed wiring board, and the caulking piece of the capsule is the second printed wiring board. An electret condenser microphone characterized in that it has a structure that is crimped to the periphery of a printed wiring board. 3. The electret condenser microphone according to claim 1, wherein an electret layer is formed on an inner surface of the closed surface of the capsule, and the electret layer and the diaphragm are opposed to each other. An electret condenser microphone characterized by a structure formed with.